1. Field of the invention
The present invention relates to a group-control method and apparatus for an elevator system with plural elevator cages, which is capable of providing the improved service for users.
2. Description of the related art
In the conventional group-control in an elevator system with plural elevator cages capable of serving plural floors of a building, for the purpose of raising the operation efficiency of an elevator system and improving the service for users, there has been used such a control method that the generation of hall calls is monitored on the on-line basis and a hall call generated at a certain floor is allotted to an adaptive cage, which is evaluated as a cage most suited for serving the certain floor, by taking account of the overall service condition to then occurring hall calls, whereby a waiting time of persons, who wait the arrival of an available cage in an elevator hall of the floor, can be shortened on a average.
According thereto, when a hall call is generated in a certain floor, it is evaluated which one of the plural cages is most suitable to serve the hall call generated, and the service to the hall call is assigned to a cage evaluated as the most suitable one. The aforesaid evaluation is carried out by calculating evaluation values of group-controlled cages with respect to the hall call generated in accordance with a predetermined evaluation function. A cage, which has a most desired one, e.g., maximum or minimum, of the calculated evaluation values, is selected as an adaptive one to serve the hall call.
The aforesaid evaluation function includes evaluation indexes of some kinds of control items as components to be considered. Such evaluation indexes are incorporated in the evaluation function with respective variable parameters, which can be altered in accordance with a traffic demand for the elevator system. The values of the parameters, which can satisfy desired targets of the control items under a certain traffic demand, are provided for every traffic demand in advance by the simulation carried out on the off-line basis or by the learning during the daily service operation.
In the daily service operation, the values of the parameters are at first selected in response to the traffic demand at that time. Since the traffic demand is provided as various patterns every time zone in a day, for example, the parameter can be changed- accordingly. Upon allotment of a hall call generated during the actual service operation, the aforesaid evaluation is carried out in accordance with the evaluation function with the selected values of the parameters. The hall call generated is allotted to an adaptive cage on the basis of the evaluation result.
For example, the laid-open Japanese patent application No. JP-A-58/52162 (1983) or 58/63668 (1983) discloses an elevator control apparatus of this kind. According thereto, the evaluation function includes an evaluation index of a stop call as well as that of a waiting time. The stop call means a call generated in a cage or a hall call already allotted to any one of the plural cages. In every cage, therefore, any cage surely stops at a floor corresponding to the stop call, i.e., a floor designated by the cage call as a destination floor or a floor, at which the hall call is generated.
With the evaluation function of the aforesaid prior art, a hall call generated becomes easily to be allotted to a cage having a stop call. As a result, the number of times of start and stop of the cages can be reduced as a whole, whereby the energy consumption is much improved, because it greatly depends on the start and stop of the cages.
The evaluation index of the stop call is incorporated in the evaluation function with a variable parameter functioning as a weight coefficient. If, therefore, the variable parameter of the stop call is adjusted, the degree of influence of the evaluation indexes of the waiting time and the stop call on the evaluation function changes relatively. This means that the service for users and the energy saving can be controlled appropriately by adjusting the variable parameter of the stop call.
However, the prior art described above scarcely took account of the point of view of an operation interval between elevator cages, whether it is a time-interval or a distance-interval. Accordingly, such an operational condition that a string of cages synchronously travel in the same traveling direction was likely to occur (this operational condition will be called a string-of-cages operation, hereinafter). The prior art was resultantly not sufficient to further improve the waiting time on an average, either.